Catalysts containing ruthenium and phosphorous have been found to promote hydrogen transfer from alcohols, other hydrocarbons, aldehydes, acids, amides and other hydrogen donors.
In an article titled "Dichlorotris(triphenylphosphine)ruthenium-catalyzed Hydrogen Transfer from Alcohols to Saturated and .alpha.,.beta.-Unsaturated Ketones", Sasson, e al. discuss the use of the ruthenium compound as an efficient catalyst for selective transfer hydrogenation of .alpha.,.beta.-unsaturated ketones by primary and secondary carbinols. In this reference kinetic studies were carried out using 1-phenyl-ethanol as a hydrogen donor and benzylideneacetophenone as an acceptor. (See J. Org. Chem. (1975), 40. 1887)
Another group has studied regioselective dehydrogenation and reported their findings in J. Org. Chem. (1986), 51. 2034. In an article titled "Ruthenium Complex Catalyzed Regioselective Dehydrogenation of Unsymmetrical .alpha.,.omega.-Diols", Ishii, et al. of the University of Tokyo, studied the ruthenium complex catalyzed regioselective dehydration of unsymmetrically substituted 1,4- and 1,5-diols in the presence of a hydrogen acceptor such as an .alpha.,.beta.-unsaturated ketone to give predominantly .beta.-substituted .gamma.-lactones and .gamma.-substituted .delta.-lactones, respectively. One of the hydrogen acceptors used was 4-phenyl-3-buten-2-one.
In an article in J. Org. Chem. (1963), 28, 448, Dillard et al. discuss various methods of preparing substituted N-(2-hydroxyalkyl)proparglyamines; and, their cyclization and subsequent hydrogenation to various morpholine derivatives is reported.
These references do not appear to discuss the synthesis of oxazine derivatives from bis-hydroxyalkylamines, nor do they discuss a novel method for using hydrogen acceptors to prevent the oxazine derivatives from being reduced to morpholine.
In related, coassigned U.S. Pat. No. 4,770,557, a method is disclosed for the preparation of hydroxymorpholines from aliphatic epoxides in the presence of a ruthenium-containing compound with a phosphine ligand at a temperature of 150.degree. C. to 190.degree. C. and a pressure of at least one atmosphere.
In a process for producing morpholines it would be an advance in the art to devise a process for alternatively producing oxazine derivatives and preventing reduction to morpholines by use of a hydrogen acceptor, particularly using mild conditions.
In the instant invention similar experimental conditions were used, as in U.S. Pat. No. 4,670,57, except a hydrogen acceptor was employed along with a ruthenium-containing compound and said acceptor functioned to prevent theoxazine derivatives (A In Eq. 1) from being reduced to morpholines.
This can be represented by the following equation: ##STR1##
Under similar conditions the N-alkyl-bis-(2-hydroxyalkyl)amines could be converted to corresponding morpholines in the absence of a suitable hydrogen acceptor, however with the hydrogen acceptor the oxazine derivatives can be produced in good yields.